In motor vehicles with a combustion engine the heater operates sufficiently as long as the quantity of heat emitted by the combustion engine is sufficient to heat the heater. However, in combustion engines having a high degree of efficiency and favorable fuel consumption behavior and thereby by the emitted heat of the combustion engine very often is not sufficient. This is particularly the case during idling and in the lower partial load range so that insufficient heat capacity for the heater noticeable ensues, particularly in lower ambient temperatures and accordingly adequate heating of the passenger cabin cannot be assured. In order to remedy this drawback, auxiliary heaters have been proposed which supplement the heating capacitor of the heater to the desired level. These auxiliary heaters operate, for example, with a fuel burner or they are operated with an electric eddy current brake.
In U.S. Pat. No. 2,749,049, wherein an eddy current brake is provided in the heating circuit which serves as a temporary auxiliary heater for the heating liquid and which is designed as an additional unit with its own drive. With such a heater, it is possible to additionally heat the heating liquid for heating purposes. However, a considerable space in the motor vehicle or on the combustion engine is required for mounting this type of heating installation